using snow to design safer streets

21 Ave & 17a St SW

By compressing the intersection into 2 small safer and more manageable intersections we are able to reclaim 3000 square feet of space. Here’s how.

Taken 4 hours after a snowfall.

Taken 4 hours after a snowfall.

Taken 4 hours after a snowfall.

Taken 4 hours after a snowfall.

Taken 4 hours after a snowfall.

This intersection has a few interesting features. For starters, a Calgary Transit bus route runs through it which is fairly odd for residential streets. It’s also an absolutely huge space. As a 4-way stop the geometry is large and stretched out. It creates a situation where crossing North-South is 50 meters and East-West is 60m. Compare that to the next intersection over, 23rd and 17a, where distances North-South are 17 meters and East West are 20m.

As a result of the extra distance and the abundance of space, you will notice the car tracks in the snow are quite varied without a clear path through the snow for each turn direction as we expect to see in well-designed streets. Predictability for all road users can lead to safety gains. The confusion demonstrated through the wide variety of tracks indicates no clear understanding of where vehicles should be in terms of lane position. In addition to this, there are 6 parking spaces for cars to park within the intersection, this complicates sight lines which is a necessity for safe operation of 4-way-stop intersections.

Considering it’s size one would assume this intersection had lots of excess space to play with. Even with all this space the intersection has no continuous sidewalk from any one corner to another. 2 of the 4 painted crosswalks lead to grass mounds.

Bottom line: There exists no way of crossing the intersection without walking on grass or along the street.

In the redesigned intersection, we take this intersection down to create T-style intersections as is the case all along 21st Ave in this neighbourhood (Sidenote: Bankview is weird with a funky grid that doesn’t line up, seemingly on purpose). By compressing the intersection in this way we regain much of the space in the intersection.

This space can be re-purposed for many things but something cheap and quick could be simply some paint, oversized flower pots and concrete barriers delineating the space with some public seating and umbrellas to provide a small neighbourhood hub or what could be considered a kind of parkette for people to enjoy. Here’s an example from NYC’s Pavement to Plazas program.

Pearl Street Pavement to Plaza Transformation in NYC

Note for the observant: Notice that the curb extension continues eastward in the design. This is to add a sidewalk where none exists. Based on a triple door garage along the street, only one car can park along this 27-meter stretch in the parking lane. In addition, the south sidewalk is dropped for that stretch only as it exists midway through the intersection and on the next block east. The street may look narrow but in reality there is already a no-parking restriction on the opposite side of the street(even if someone is illegally parked there in google maps). This width can handle two-way traffic only.